19 Aug
2024
19 Aug
'24
3:14 p.m.
On Mon, Aug 19, 2024 at 10:17:52AM +0100, Catalin Marinas wrote:
On Thu, Aug 01, 2024 at 01:06:45PM +0100, Mark Brown wrote:
+static bool is_invalid_gcs_access(struct vm_area_struct *vma, u64 esr) +{
- if (unlikely(is_gcs_fault(esr))) {
/* GCS accesses must be performed on a GCS page */if (!(vma->vm_flags & VM_SHADOW_STACK))return true;if (!(vma->vm_flags & VM_WRITE))return true;
Do we need the VM_WRITE check here? Further down in do_page_fault(), we already do the check as we set vm_flags = VM_WRITE.
if (!(vma->vm_flags & vm_flags)) { vma_end_read(vma); fault = 0;
It looks bitrotted, yes.
I was wondering whether we should prevent mprotect(PROT_READ) on the GCS page. But I guess that's fine, we'll SIGSEGV later if we get an invalid GCS access.
Yeah, that doesn't seem like a particular problem - the concern is adding rather than removing GCS.